Introduction

The snail-case caddisflies of the family Helicopsychidae were first recognized as the subfamily Helicopsychinae of Sericostomatidae by Ulmer (1906) and were retained there by a number of European workers well into the 1950s, most notably Ulmer himself (Ulmer 1955). Ross (1944) and other American workers considered the group a distinct family, reflecting its current status. As presently constituted, the family contains only 2 genera, the cosmopolitan Helicopsychevon Siebold with about 250 species, and the New Zealand endemic genus Rakiura McFarlane, with a single species, R. vernale McFarlane. Several previously recognized genera, including Cochliopsyche Müller (Neotropical), Petrotrichia Ulmer (Afrotropical, including Madagascar and the Seychelles, but absent from southern Africa), and Saetotrichia Brauer (Australia, New Zealand, New Caledonia), were relegated as subgenera of Helicopsyche by Johanson (1998). In the same paper, Johanson described 2 additional subgenera of Helicopsyche: Feropsyche (Nearctic, Neotropical) and Galeopsyche(Korea, Vietnam). The nominotypical subgenus occurs in the Palearctic and Oriental regions. As a whole the family is poorly represented in the Northern Hemisphere, but reaches its greatest diversity in the tropics of the Old and New Worlds (Johanson 1997); the Neotropics alone hosts about 100 species. Taken from Holzenthalet al. (2007).

Characteristics

Larvae of the genus are the familiar and remarkable snail-case builders. These helical, sand grain cases are so similar to snails that early workers described these insects as molluscs. Lea (1834) went so far as to say of Valvata arenifera(=Helicopsyche borealis), “It has the singular property of strengthening its whirls by the agglutination of particles of sand, and by which it is entirely covered.” While all helical, there is great diversity in the height of cases, the number and openness of the whorls, the size of mineral material, and the amount of silk incorporated. All helicopsychid larvae appear to feed as scrapers on periphyton and other organic matter on the exposed surfaces of rocks. They are found in slow flowing lowland streams as well as springs, small fast-flowing streams, and the wave-washed shores of lakes in temperate regions; they also occur in the hyporheic zone (Williams et al. 1983) and in thermal springs (Resh et al. 1984). The biology of the North American species, H. borealis (Hagen) is well known (Vaughn 1985a, b, 1987). Taken from Holzenthal et al. (2007).

An interesting and potential case of mimicry. Or just a possibility for confusion. Some of these caddisfly shells have already been spotted in a malacological collection, so curators may want to check their holdings…